Photocatalytic reduction of nitrate ions in water over metal-modified TiO2

Abstract TiO 2 and TiO 2 doped with Zn 2+ , Cu 2+ and Cr 3+ were used as photocatalysts to reduce nitrate and to oxidize formic acid. The metals were added to the TiO 2 support by photodeposition and this method did not affect the form of the original crystalline semiconductor (100% anatase). The data obtained in the structural characterization and in the nitrate photoreduction experiments showed that 1.0 g L −1 4.4% Zn–TiO 2 photocatalyst had the highest photocatalytic activity and selectivity toward nitrogen. The selectivity and conversion were higher than 95 and 91%, respectively, using a CHOOH:nitrate molar ratio of 16:1, which is twice the theoretical demand in the absence of dissolved oxygen.